Diff re-seal

[The Veg]

Now that I've driven the Plus 2 a few hundred miles since getting it back to operability, I'm fairly certain that the diff is leaking. The thick buildup of dirt stuck in oil is one clue, as is some fresh oil in a couple of places. Since I'm going to be swapping transmissions soon, I'm thinking that during that process might be a good time to pull the diff and replace seals. I've read that getting the thing out of the car is a pig of a job, so I'm expecting that. How easy is it to do the seals once it's out? Any special precautions or things to check during the job?

[Hawksfield]

Veg

If its leaking from the drive shaft bearings this can be done insitu, if however its from the diff to transaxle case seal the diff will have to be removed.

Diff removal on mine is easy to remove but more difficult to put back on my own but doable (Three times) make sure you warm the alloy casing before pulling the drive shafts. I use an old Lotus drive shaft and three long bolts as a slide hammer.

My slide hammer

[mbell]

Any clue where it is leaking from? Pinion? Drive shafts? filler/drain plugs? case join?

Removal requires removing at least the drive shafts, fuel tank and a rear lower arm. The prop shaft also need disconnecting along with rest of the diff mounts.

I am about to pull mine any day as part of bigger rear end refresh, I have the full rear suspension removed from the car as part of that. I do have the Rdent drive shafts so will see if i can get it out with shafts attached or not.If not it will likely delay things quite a bit.

[gjz30075]

Ben, check this out from our forum member Col
https://www.youtube.com/watch?v=-12F0s58y6k

The tricks at 2:10 through 2:55 or so did the trick for me.

[The Veg]

Thanks for the tips.

Leaks seem to be at the input seal for sure and at least one output seal. Plugs seem OK. Can't recall off the top of my head whether or not anyplace else is suspect.

Interesting slide-hammer idea. I do have the old shafts so that should be easy to set up.

[mbell]

I believe the output shafts ones are just rubber lip seals fitted just inboard of the outer shaft bearing. So just require removal of the outptu shafts from teh diff.

The input/pinion one is more complex, the pinion flange need to be removed. The nut holding the pinion flange also affects the diff preload, so care needs to be taken, Have a look at:
viewtopic.php?f=37&t=41056

[The Veg]

Thanks, good reading. Should be an interesting job in any case.

[The Veg]

Just a small update; I've got the diff removed from the car and it really wasn't all that difficult. I could see that the mod to remove some metal under the nose to make getting it in and out had NOT been done, but it still only needed a little jiggling to drop right out. Maybe all that oily muck lubricated it enough to come freely!

So now the task at hand is getting the outside cleaned. Nothing has been taken loose as yet; I'm just cleaning it fully assembled before attempting the seals. I've got the main part mostly clean and will soon start on the nose- am I correct that the nose is iron?. Interestingly, there's a fair amount of body-colour paint on the nose. The backside of the housing had a solid quarter-inch of hardened oily muck in some places on it. Nothing that a plastic scraper, an old toothbrush and a can of penetrating oil can't overcome though!

[jono]

I've literally (yesterday) completed my diff overhaul so feel free to ask any questions while it's fresh in my mind.

I replaced the output seals, the pinion seal and the output bearings and obtained all the parts from Sue Miller.

I punched the pinion nut and pinion end so that they could go back to the original position to maintain pre load - I was happy to note they lined up exactly as the torque wrench hit 35 lb ft. I washed the splines and nut/threads with brake cleaner and used some Loctite black silicone to seal it - the nut has an internal chamfer and I wonder if this is deliberate to accomodate some of the sealant as it compresses? (which incidentally I kept off the clamping face).

I used Sue's gasket as supplied and Aviation Nr 3 gasket maker on both faces between the diff and cover (a very fine smear). The output bearings were a good interference fit to the cover but I still applied some bearing fit and warmed the housing.

The output seals were pressed in with a socket and pump action clamp - this worked well. I put some Redline assembly lube on all seal faces before fitting.

I used a little thread lock on the cover bolts as well and torqued to 15 lb ft - the diff casting was painted with a couple of coats of red lead as original. I'm happy with it all - another mini project completed as part of the resto.

[mbell]

I also did a smaller version of this recently, just a clean, paint and pinion seal. I used wire wheel ion grinder to clean up the housings. Then a coat of POR15 on the nose housing (and brace).

For the pinion seal I marked the shaft,nut and pinon with a sharpie. I took some photo's so could clearly see the number of threads the nut was on. Removed and replaced the seal, for this I drill a couple of holes and screwed in screws so i could pull the seal. There is a small area behind the seal so the very small amount of swarf was easy to clean up.I used a piece of wood and hammer to know the new seal in place (after lubing the lip). Then assembled back together.

I used a little thread sealer on the underside of the washer and also on the bottom of the nut, to help prevent and leaks down the shaft. Then replaced the nut back to the original position.

Diff is not fitted so can't be sure there are no issues, but it feels fine and as it did before.

[SENC]

Interestingly, there's a fair amount of body-colour paint on the nose.

I recall reading somewhere, but can't find it now, that the sides of the diff (btw the webs) were painted yellow to indicate a 3.77.

[Bigbaldybloke]

Sounds like you are progressing well so far, one thing you may want to do is fit the diff strengthening bar mod as you refit the diff. Pretty straightforward to do if you already have the diff out. Good luck with the work, hopefully a straightforward seal replacement job.

[2cams70]

I used a little thread sealer on the underside of the washer and also on the bottom of the nut, to help prevent and leaks down the shaft. Then replaced the nut back to the original position.

The leaks on pre around 1973 differentials around the pinion flange down the splines is caused by a combination of inadequately designed preload crush tube and retaining nut. Post 1973 diffs (in Ford application at least) had crush tubes with thicker walls and much stiffer retaining nuts that don't loose tension. The earlier crush tubes collapsed over time and the nuts came loose. This resulted in loss of bearing preload and leaks down the spline.

Whenever you're removing the flange you are best off replacing these parts with the later design. All the new parts you can buy from the likes of Burton's etc. are to this specification. Does mean you have to reset the pinion bearing preload of course.

[mbell]

Thanks for the information, very interesting. I did buy the crush tube but decided it was best not to mess around with it.

The car is a late 73 and there was no signs of leaking down the shaft. So maybe it has the updated parts. The thread sealer was mostly precautionary, after reading of issues on here.

[The Veg]

Interestingly, there's a fair amount of body-colour paint on the nose.

I recall reading somewhere, but can't find it now, that the sides of the diff (btw the webs) were painted yellow to indicate a 3.77.

I didn't know that but it makes sense, and now that most of the crud is removed that's exactly where the paint is- definitely not any type of overspray, not that it would get all the way up in there anyway.

I think I've removed five pounds of crud.